1. Field of the Invention
The present invention relates to a recording method, and more particularly to the recording method by which while the recording head, having the dot forming element array in which N (N is a positive integer) dot forming elements are aligned at intervals of an even multiple of the distance d between dots in the recording resolution R in the secondary scanning direction which is the direction of conveyance of a recording material, is reciprocally moved in the primary scanning direction perpendicular to the secondary scanning direction, dots are formed on the recording material by the dot forming element array in accordance with recording data, and also the recording material is conveyed in the secondary direction and relatively to the recording head, thus performing recording. Also, the invention relates to a recording apparatus.
The present application is based on Japanese Patent Applications No. 2000-221965 and 2001-210857, which are incorporated herein by reference.
2. Description of the Related Art
In a recording apparatus, e.g., the ink jet printer for performing color printing, the recording head including a plurality of nozzles (dot forming elements) from which ink droplets are ejected, while being reciprocally moved in a primary scanning direction, ejects ink droplets, and also printing paper (a recording material) is conveyed relatively to the recording head and in the secondary scanning direction perpendicular to the primary scanning direction, whereby printing (recording) is performed.
On the recording head, the nozzle (dot forming element) arrays which eject the respective inks of black, dark cyan, light cyan, dark magenta, light magenta, and yellow are disposed in this order in the primary scanning direction.
As the recording method aimed at improving the recording quality of such a color ink jet printer, there is a recording method called the interlacing method described in U.S. Pat. No. 4,198,642 and Unexamined Japanese Patent Publication No. Sho. 53-2040.
In the printing by this xe2x80x9cinterlacing methodxe2x80x9d, while rasters are formed (i.e. printed) intermittently in the secondary scanning direction, an image is recorded. Then, adjacent rasters are bound to be formed by different nozzles.
However, when the conventional interlacing method is used for the bidirectional printing in which printing is performed on both the forward and backward trips in the primary scanning direction, after a certain raster is formed, the printing paper (recording material) is conveyed in the secondary scanning direction and relatively to the recording head, and thereafter the next raster is formed, whereupon the directions of movement of the recording head in both rasters are reversed to each other. Namely, a certain raster is formed on the forward trip in the primary scanning direction, whereas the next raster is formed on the backward trip in the primary scanning direction.
Therefore, in both rasters, the order of the nozzles from which ink droplets are ejected is reversed. Namely, for example, on the forward trip, ink droplets are ejected in the order of black, dark cyan, light cyan, dark magenta, light magenta, and yellow, whereas on the backward trip, ink droplets are ejected in the reverse order thereto of yellow, light magenta, dark magenta, light cyan, dark cyan, and black. Consequently, in every conveyance unit in the secondary scanning direction, striping (a kind of so-called banding) tends to be visibly generated.
In order to prevent such generation of striping, there is proposed the full-overlap recording method by which a plurality of dots constituting one raster are formed intermittently on each of the forward and backward trips. However, in this recording method, there is a problem that the respective rasters are formed on the forward and backward trips, so that printing speed (throughput) is reduced.
On the other hand, in the ink jet printer in which pigment is used as ink, the dot diameter formed by ink droplets tends to be smaller than that in case of using dye as ink. Consequently, the width (so-called line width) of the raster formed by aligning a plurality of dots in the primary scanning direction also tends to be narrower. Also, each nozzle normally has the deflection (so-called flying curve) peculiar to the nozzle, and ink droplets are not always ejected perpendicularly with respect to the recording head surface on which nozzles are disposed. In this flying curve, there are a flying curve in the secondary scanning direction and a flying curve in the primary scanning direction.
As in the interlacing method, when the adjacent rasters are printed by different nozzles, depending upon the degree of the flying curve in the secondary scanning direction of the nozzles, the gap (i.e. the so-called white stripe in which the ground of printing paper remains unprinted) which is not filled with ink droplets is sometimes produced between both rasters. For example, when a certain raster and the raster adjacent thereto are formed by the nozzles having the flying curves in the directions backing away from each other, the space between both rasters becomes wider than an ideal space, so that a white stripe is generated between both rasters.
Theoretically, if the dot diameter is set to the value (hereinafter referred to as a xe2x80x9ctheoretical value of dot diameterxe2x80x9d) obtained by multiplying the interval d between dots by a square root of two, printing can be performed without a white stripe generated. On the other hand, in the actual ink jet printer, since the flying curve in the secondary scanning direction is present, in consideration thereof, the dot diameter is set to the order of twice as large as the interval d between dots, thereby preventing the generation of a white stripe.
In the conventional ink using dye, since the dot diameter becomes in the order of twice as large as the interval d between dots, even if any flying curve in the secondary scanning direction is present, there is no possibility that a white stripe is generated. On the other hand, in the pigment ink, although the dot diameter is larger than the theoretical value of dot diameter, it is smaller than twice the interval d between dots, so that depending upon the degree of the flying curve in the secondary scanning direction, there is a possibility that a white stripe is generated.
The invention is made in light of these circumstances, and its first object is to provide the recording method and the recording apparatus in which by improving the interlacing method, in the bidirectional recording, no striping is generated, and further, recording is possible at a higher speed than in the conventional full-overlap recording method.
Also, the invention has for its second object the arrangement that even in case the dot diameter becomes smaller as in the pigment ink, a so-called white stripe is not generated.
In order to attain the first object and a portion of the second object, the recording method according to a first aspect of the invention, in the recording method by which, while the recording head, having the dot forming element array in which N (N is a positive integer) dot forming elements are aligned at constant intervals D in the secondary scanning direction which is the direction of conveyance of a recording material, is reciprocally moved in the primary scanning direction perpendicular to the secondary scanning direction, dots are formed on the recording material by the dot forming element array in accordance with recording data, and the recording material is conveyed in the secondary direction and relatively to the recording head, is characterized in that the interval D is the value obtained by multiplying the interval d between dots in the recording resolution in the secondary scanning direction by an even number k, and also the even number k and the dot forming element number N are in prime relation to each other, that there are included a first step of forming dots on the recording material by the dot forming element array while moving the recording head along the forward-trip path in the primary scanning direction, a second step of conveying the recording material in the secondary direction and relatively to the recording head by a secondary scanning distance of the interval d between dots, a third step of forming dots on the recording material by the dot forming element array while moving the recording head along the backward-trip path in the primary scanning direction, and a fourth step of conveying the recording material in the secondary scanning direction and relatively to the recording head by a secondary scanning distance of (2Nxe2x88x921) d, and that the first to fourth steps are repeated, thereby performing recording.
According to the recording method of the first aspect of the invention, by the first step, N rasters are formed on the forward trip in the primary scanning direction, whereafter by the second and third steps, the next N rasters adjacent these N respective rasters are formed on the backward trip in the primary scanning direction. These N rasters formed on the forward trip and the next N rasters formed on the backward trip are formed by the same dot forming elements. Namely, the recording on the recording material is performed in units of two adjacent rasters formed respectively on the forward and backward trips Therefore, the entire image thus recorded is formed in units of these two adjacent rasters, so that in the conventional interlacing method, in case the bidirectional recording is performed, the striping to be generated in every conveyance unit in the secondary scanning direction can be prevented in the entire image.
Also, each raster is formed through the recording on either the forward or backward trip by the same dot forming elements, thus enabling higher-speed printing than in the conventional full-overlap recording method.
Further, between two rasters formed by the same dot forming elements, since the dot forming elements for forming these two rasters are the same, the flying curves in the secondary scanning direction are also made the same. Namely, these two rasters, even if any flying curves in the secondary scanning direction are present, are curved in the same direction. Therefore, if the dot diameter is in the order of the theoretical value of dot diameter, a white stripe is never generated between both rasters. Consequently, even in case the invention is used for the ink jet printer using pigment ink, the generation of a white stripe between dots can be prevented between these two rasters.
The recording method according to a second aspect of the invention, in the recording method by which, while the recording head, having the dot forming element array in which N (N is a positive integer) dot forming elements are aligned at constant intervals D in the secondary scanning direction which is the direction of conveyance of the recording material, is reciprocally moved in the primary scanning direction perpendicular to the secondary scanning direction, dots are formed on the recording material by the dot forming element array in accordance with recording data, and the recording material is conveyed in the secondary direction and relatively to the recording head, is characterized in that the interval D is the value obtained by multiplying the interval d between dots in the recording resolution in the secondary scanning direction by an even number k, and also the even number k and the dot forming element number N are in prime relation to each other, that there are included a first step of forming dots on the recording material by the dot forming element array while moving the recording head along the forward-trip or backward-trip path in the primary scanning direction, a second step of conveying the recording material in the secondary direction and relatively to the recording head by the secondary scanning distance of the interval d between dots, a third step of forming dots on the recording material by the dot forming element array while moving the recording head along the forward-trip or backward-trip path in the primary scanning direction, and a fourth step of conveying the recording material in the secondary scanning direction and relatively to the recording head by a secondary scanning distance of (2Nxe2x88x921)xc2x7d, and that the first to fourth steps are repeated, thereby performing recording.
According to the invention, also in a unidirectional recording instead of the bidirectional recording, an image is formed in units of two adjacent rasters. Therefore, between two rasters formed by the same dot forming elements, since the dot forming elements for forming these two rasters are the same, the flying curves in the secondary scanning direction are also made the same. Namely, these two rasters, even if any flying curves in the secondary scanning direction are present, are curved in the same direction. Therefore, if the dot diameter is in the order of the theoretical value of dot diameter, a white stripe is never generated between both rasters. Consequently, even in case the invention is used for the ink jet printer using pigment ink, the generation of a white stripe between dots can be prevented between these two rasters.
The recording method according to a third aspect of the invention, in the recording method according to the first or second aspect, is characterized in that two adjacent rasters formed by the same dot forming elements before and after the secondary scanning distance d relative conveyance are made one unit, and another raster adjacent the rasters constituting one unit is formed by the different dot forming elements from the dot forming elements used for forming the unit raster.
The recording method according to a fourth aspect of the invention, in the recording method according to the first or second aspect, is characterized in that the recording head further has M (M is a positive integer not more than N) auxiliary dot forming element arrays aligned at the intervals D in the secondary scanning direction at the upstream-side end portion or downstream-side end portion in the secondary scanning direction of the N dot forming element arrays, and that the auxiliary dot forming element arrays and the M dot forming element arrays at the downstream-side end portion out of the N dot forming element arrays in case the auxiliary dot forming element arrays are disposed at the upstream-side end portion, and the auxiliary dot forming element arrays and the M dot forming element arrays at the upstream-side end portion out of said N dot forming element arrays in case the auxiliary dot forming element arrays are disposed at the downstream-side end portion, form dots intermittently in proper quantities on the same primary scanning line in both the first step and the third step so that dots are not formed so as to be superposed on each other at the same position, or there is not produced the place in which no dots are formed at the position where dots are to be formed.
According to the recording method of the fourth aspect of the invention, by the secondary scanning distance (2Nxe2x88x921)xc2x7d conveyance, the dot forming position of M auxiliary dot forming element arrays and the dot forming position of M out of N dot forming elements arrays come to be overlapped. Both these dot forming element arrays form dots intermittently in proper quantities so that dots are not formed so as to be superposed on each other at the same position, and there is not produced the place in which not dots are formed at the position where dots are to be formed. Therefore, the partial dots in M rasters are formed before the secondary scanning distance (2Nxe2x88x921)xc2x7d conveyance, and the remaining dots are formed after the conveyance by the same secondary scanning distance. Thereby, the banding generated every time the recording paper is relatively moved in the secondary scanning direction by the conventional interlacing method can be made inconspicuous, and image quality can be improved.
The recording method according to a fifth aspect of the invention, in the recording method according to the fourth aspect, is characterized in that the M auxiliary dot forming element arrays and M out of the N dot forming element arrays form dots intermittently at a ratio of one to one.
According to the recording method of the fifth aspect of the invention, since the ratio of intermittent dot formation is one to one, the driving control of the recording head can be made simple.
The recording method according to a sixth aspect of the invention, in the recording method according to the first or second aspect, is characterized in that when the offset xcex1 of a secondary scanning distance is defined as a greater value than zero, and also as a value not more than the value obtained such that the value obtained by multiplying the interval d by a square root of two is subtracted from the dot diameter formed by the dot forming elements, and the value resulting from the subtraction is divided by a square root of two, the secondary scanning distance in the second step is the distance obtained by adding the offset xcex1 to the distance d, and the secondary scanning distance in the fourth step is the distance obtained by subtracting the offset xcex1 from the distance (2Nxe2x88x921)xc2x7d.
Two adjacent rasters formed by the same dot forming elements, even if any flying curves are present, are curved in the same direction, so that the interval x between both rasters can be set up to the order of the value obtained by dividing the actual dot diameter a by a square root of two. In other words, even if the actual dot diameter a is a theoretical value of dot diameter (=xxc3x97a square root of two) with respect to the interval x between both rasters (i.e. the interval between dots), recording becomes possible without a white stripe generated between both rasters.
Therefore, when the maximum value of offset to be added to the interval between rasters is set to xcex1 MAX, even if the interval x between both rasters is set to
d less than xxe2x89xa6d+xcex1MAX
where
xcex1MAX={(actual dot diameter a)xe2x88x92interval dxc3x97(a square root of two)}÷(a square root of two),
recording can be performed without a white stripe generated between both rasters.
If the offset xcex1 is set to 0 less than xcex1xe2x89xa6xcex1 MAX, according to the recording method of the fourth aspect of the invention, the interval between the rasters formed by the same dot forming elements is set to d+xcex1. Hence, on one hand, a white stripe is not generated between both rasters, and on the other hand, the interval between rasters is widened. Thus, even in case the dot diameter formed by the dot forming elements is relatively small, the width (line width) of the image formed by two adjacent rasters can be made wider.
On the other hand, the distance between rasters after the secondary scanning distance (2Nxe2x88x921)xc2x7d movement is made smaller by a. The raster formed before secondary scanning distance {(2Nxe2x88x921)xc2x7dxe2x88x92xcex1} movement and the raster adjacent thereto formed after the secondary scanning distance {(2Nxe2x88x921)xc2x7dxe2x88x92xcex1} movement are formed by different dot forming elements. Therefore, if the actual dot diameter is less than twice the interval d, a white stripe is possibly generated. However, the secondary scanning distance is made smaller by xcex1, so that even in case the actual dot diameter is less than twice the interval d, the generation of a white stripe between both rasters can be suppressed. Thereby, both between two rasters formed by the same dot forming elements and between two rasters formed by different dot forming elements, the generation of a white stripe is suppressed. Thus, the second object of the invention is achieved.
The recording method according to a seventh aspect of the invention, in the recording method according to the first or second aspect, is characterized in that the secondary scanning distance in the second step is the distance obtained by adding the offset xcex1 to the distanced, the secondary scanning distance in the fourth step is the distance obtained by subtracting the offset xcex1 from the distance (2Nxe2x88x921)xc2x7d, and the offset xcex1 of a secondary scanning distance is a greater value than zero, and also is the value at which no white stripe is generated either between the adjacent rasters formed before and after secondary scanning distance (d+xcex1) movement or between the rasters formed before and after the secondary scanning distance {(2Nxe2x88x921)xc2x7dxe2x88x92xcex1} movement.
Also according to the invention, the effect similar to that of the sixth aspect of the invention can be obtained.
The recording method according to the invention of an eighth aspect, in the recording method according to the first or second aspect, is characterized in that the recording data for forming dots in the first step and the recording data for forming dots in the third step are the same.
According to the recording method of the eighth aspect of the invention, since the recording data in the first and third steps are the same, the recording data can be reduced to one second. Thereby, the time period required for recording data generation processing is also reduced, and the entire recording can be performed at a high speed.
The recording method according to a ninth aspect of the invention, in the recording method according to the sixth aspect, is characterized in that the recording data for forming dots in the first step and the recording data for forming dots in the third step are the same.
The recording apparatus according to a tenth aspect of the invention, in the recording apparatus which includes the recording head having the dot forming element array in which N (N is a positive integer) dot forming elements are aligned at constant intervals D in the secondary scanning direction which is the direction of conveyance of the recording material, the head driving means for driving the dot forming elements, the primary scanning driving means for reciprocally moving the recording head in the primary scanning direction perpendicular to the secondary scanning direction with respect to said recording material, the secondary scanning driving means for conveying the recording material in the secondary scanning direction and relatively to the recording head, the control means for controlling the head driving means, the primary scanning driving means, and the secondary scanning driving means, and performs recording while the recording head scans the surface of the recording material in the primary scanning direction and the secondary scanning direction, is characterized in that the interval D is the value obtained by multiplying the interval d between dots in the recording resolution in the secondary scanning direction by an even number k, and also the even number k and the dot forming element number N are in prime relation to each other, and that recording is performed by such repetition that the control means controls the primary scanning driving means and the head driving means to form dots on the recording material by the dot forming element array while moving the recording head along the forward-trip path in the primary scanning direction, controls the secondary scanning driving means to convey the recording material in the secondary direction and relatively to the recording head by a secondary scanning distance of the interval d between dots, controls the primary scanning driving means and the head driving means to form dots on the recording material by the dot forming element array while moving the recording head along the backward-trip path in the primary scanning direction, and controls the secondary scanning driving means to convey the recording material in the secondary scanning direction and relatively to the recording head by a secondary scanning distance of (2Nxe2x88x921)xc2x7d.
According to the recording apparatus of the tenth aspect of the invention, the effect similar to that of the first aspect of the invention can be obtained.
The recording apparatus according to an eleventh aspect of the invention, in the recording apparatus which includes the recording head having the dot forming element array in which N (N is a positive integer) dot forming elements are aligned at constant intervals D in the secondary scanning direction which is the direction of conveyance of the recording material, the head driving means for driving the dot forming elements, the primary scanning driving means for reciprocally moving the recording head in the primary scanning direction perpendicular to the secondary scanning direction with respect to the recording material, the secondary scanning driving means for conveying the recording material in the secondary scanning direction and relatively to the recording head, the control means for controlling the head driving means, the primary scanning driving means, and the secondary scanning driving means, and performs recording while the recording head scans the surface of the recording material in the primary scanning direction and the secondary scanning direction, is characterized in that the interval D is the value obtained by multiplying the interval d between dots in the recording resolution in the secondary scanning direction by an even number k, and also the even number k and the dot forming element number N are in prime relation to each other, and that recording is performed by such repetition that the control means controls the primary scanning driving means and the head driving means to form dots on the recording material by the dot forming element array while moving the recording head along the forward-trip or backward-trip path in the primary scanning direction, controls the secondary scanning driving means to convey the recording material in the secondary direction and relatively to the recording head by a secondary scanning distance of the interval d between dots, controls the primary scanning driving means and the head driving means to form dots on the recording material by the dot forming element array while moving the recording head along the forward-trip or backward-trip path in the primary scanning direction, and controls the secondary scanning driving means to convey the recording material in, the secondary scanning direction and relatively to the recording head by a secondary scanning distance of (2Nxe2x88x921)xc2x7d.
The recording apparatus according to a twelfth aspect of the invention, in the recording apparatus according to the tenth or eleventh aspect, is characterized by being arranged that two adjacent rasters formed by the same dot forming elements before and after the secondary scanning distance d relative conveyance are made one unit, and another raster adjacent the rasters constituting one unit is formed by the different dot forming elements from the dot forming elements used for forming the unit raster.
The recording apparatus according to a thirteen aspect of the invention, in the recording apparatus according to the tenth or eleventh aspect, is characterized by being arranged that the recording head further has M (M is a positive integer not more than N) auxiliary dot forming element arrays aligned at the intervals D in the secondary scanning direction at the upstream-side end portion or downstream-side end portion in the secondary scanning direction of the N dot forming element arrays, and that the auxiliary dot forming element arrays and the M dot forming element arrays at the downstream-side end portion out of the N dot forming element arrays in case the auxiliary dot forming element arrays are disposed at the upstream-side end portion, and the auxiliary dot forming element arrays and the M dot forming element arrays at the uptream-side end portion out of the N dot forming element arrays in case the auxiliary dot forming element arrays are disposed at the downstream-side end portion, form dots intermittently in proper quantities on the same primary scanning line by the control means in both the first step and the third step so that dots are not formed so as to be superposed on each other at the same position, or there is not produced the place in which no dots are formed at the position where dots are to be formed.
The recording apparatus according to a fourteenth aspect of the invention, in the recording apparatus according to the thirteenth aspect, is characterized by being arranged that the M auxiliary dot forming element arrays and M out of the N dot forming element arrays form dots intermittently at a ratio of one to one.
The recording apparatus according to a fifteenth aspect of the invention, in the recording apparatus according to the tenth or eleventh aspect, is characterized in that when the offset a of a secondary scanning distance is defined as a greater value than zero, and also as a value not more than the value obtained such that the value obtained by multiplying the interval d by a square root of two is subtracted from the dot diameter formed by the dot forming elements, and the value resulting from the subtraction is divided by a square root of two, the control means is arranged such that the secondary scanning distance in the second step is the distance obtained by adding the offset xcex1 to the distance d, and the secondary scanning distance in the fourth step is the distance obtained by subtracting the offset xcex1 from the distance (2Nxe2x88x921)xc2x7d.
The recording apparatus according to a sixteenth aspect of the invention, in the recording apparatus according to the tenth or eleventh aspect, is characterized by being arranged that the secondary scanning distance in the second step is the distance obtained by adding the offset xcex1 to the distance d, the secondary scanning distance in the fourth step is the distance obtained by subtracting the offset xcex1 from the distance (2Nxe2x88x921)xc2x7d, and the offset a of a secondary scanning distance is a greater value than zero, and also is the value at which no white stripe is generated either between the adjacent rasters formed before and after the secondary scanning distance (d+xcex1) movement or between the rasters formed before and after the secondary scanning distance {(2Nxe2x88x921)xc2x7dxe2x88x92xcex1} movement.
The recording apparatus according to the invention of a seventeenth aspect, in the recording apparatus according to the tenth or eleventh aspect, is characterized in that the control means is set or can be set such that the recording data for forming dots in the first step and the recording data for forming dots in the third step are the same.
The recording apparatus according to an eighteenth aspect of the invention, in the recording apparatus according to the fifteenth aspect, is characterized in that the control means is set or can be set such that the recording data for forming dots in the first step and the recording data for forming dots in the third step are the same.
Features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with the attached drawings.